Correlations in quantum states and the local creation of quantum discord

: Gessner M, Laine EM, Breuer HP, Piilo J

Publisher: AMER PHYSICAL SOC

: 2012

: Physical Review A

: PHYSICAL REVIEW A

: PHYS REV A

: ARTN 052122

: 5

: 85

: 5

: 4

: 1050-2947

DOI: https://doi.org/10.1103/PhysRevA.85.052122

: https://arxiv.org/abs/1202.1959

Quantum discord is usually referred to as a measure for quantum correlations. In the search of the fundamental resource to gain a quantum advantage in quantum information applications, quantum discord is considered a promising candidate. In this paper we present an alternative view on quantum correlations in terms of the rank of the correlation matrix as introduced by Dakic, Vedral, and Brukner [Phys. Rev. Lett. 105, 190502 (2010)]. According to our analysis, information about the quantum discord does not necessarily determine the amount of quantum correlations but rather the quantumness of the state. Nonzero quantum discord is only a necessary but not a sufficient condition for correlations above the classically achievable limit. This becomes clear when we consider states of nonzero discord, which can be created from zero discord states only by a single local operation. We further show that the set of these states has measure zero.